arm64: dts: marvell: AC5/AC5X: Fix address for UART1

The correct address offset is 0x12100.

Fixes: 31be791e

 ("arm64: dts: marvell: Add UART1-3 for AC5/AC5X")
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>